X-ray or gamma ray systems or devices – Source – Electron tube
Reexamination Certificate
1999-01-25
2001-02-13
Porta, David P. (Department: 2876)
X-ray or gamma ray systems or devices
Source
Electron tube
C378S119000, C378S121000
Reexamination Certificate
active
06188747
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an X-ray generator having a first high-voltage source and an X-ray tube which is provided with an anode, a first cathode and a second cathode which is electrically independent from the first cathode. A first high voltage supplied by the first high-voltage source is applied to a first system formed by the anode and the first cathode to obtain a first X-ray radiation. Further, the X-ray generator includes a second high-voltage source which delivers a high voltage different from the first high voltage.
Current X-ray apparatus used in security systems for examining freight and packages, are capable of distinguishing materials from one another, in addition to producing a shadow image of the contents. For such an operation the object under examination has to be irradiated with X-ray beams having two different discreet energy levels or energy level ranges. According to a technical solution, two sequential fan-shaped X-ray beams are generated which consecutively pass through the object. The energy levels of the fan-shaped beams are different, and thus a comparison of the spectra to be examined and derived from the object leads to a material classification.
For effecting a classification of material, it is known to arrange mechanically side-by-side two X-ray tubes for X-ray generators having different limit energy levels. For reasons of mechanical and high-voltage technology such X-ray generators require a certain minimum volume, and therefore the distance between the two fan-shaped beams has a minimum limit value which cannot be reduced. Such a circumstance, however, leads to technological disadvantages, particularly caused by mechanical tolerances, drifts in temperature and wear which lead to erroneous measuring data and thus adversely affect the accuracy of the measuring system.
German Patent No. 3,635,395 discloses an X-ray generator for producing at least two different X-ray radiations. The X-ray tube of the generator has at least two mutually independent cathodes which cooperate with an anode at different high voltages. Two or more X-ray beams are generated at different locations on a side of the anode.
German Offenlegungsschrift (application published without examination) No. 31 39 899 discloses an X-ray tube having two annular anodes and a cathode arrangement which encircles the anodes. In the annular anodes an opening is provided into or between which the material to the examined may be introduced.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an improved X-ray generator with which a material classification for objects to be X-rayed is simplified.
This object and others to become apparent as the specification progresses, are accomplished by the invention, according to which briefly stated, an X-ray generating system includes a first high-voltage source generating a first high voltage; a second high-voltage source generating a second high voltage different from the first high voltage; and an X-ray generator. The X-ray generator includes a first assembly having a first cathode and a first anode for emitting a first X-ray beam from a first focal point on the first anode upon application of the first high voltage to the first assembly. The X-ray generator further includes a second assembly having a second cathode and a second anode for emitting a second X-ray beam from a second focal point on the second anode upon application of the second high voltage to the second assembly. The two X-ray beams exit the X-ray generator parallel to one another.
The invention is based on the principle to provide an X-ray generator having two cathode systems and two anode systems to obtain two internal, mutually separate radiation sources. The anode systems are integrated in an anode head which is preferably a copper block situated between the two cathode systems. The cathode systems each include a conventional heating filament for the electron emission and an electrostatic lens.
By applying different high voltages to the bremsstrahlung (braking radiation) sources, different energy spectra are generated on the anodes. In this manner two radiation sources are provided which are distinctly defined and locally separated from one another and are nevertheless situated closely side-by-side. A shielding hood prevents a mutual interference or cross-mixing of the two radiation levels or radiation ranges. Mechanical tolerances of the two radiation systems are small and reproducible because of the common structure. The mechanical dimensions of the two-beam system are significantly reduced.
By virtue of the construction of the X-ray generator as a dual energy X-ray generator according to the invention, a dual focusing system is provided which may be positioned as closely as 20 mm from one another. Apart from a more accurate measurement, such an arrangement also achieves a shorter run-through period for the objects to be examined since the distance of the fan-shaped X-ray beams from one another is reduced. In addition, an in situ setting is significantly simplified. Also, an adjustment of the X-ray radiations with respect to one another is dispensed with.
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Foos Kurt
Geus Georg
Heimann Systems GmbH
Ho Allen C.
Kelemen Gabor J.
Porta David P.
Venable
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